staging: mt7621-dma: Remove print statement on devm_kzalloc error

Remove print statement following error of devm_kzalloc. Issue found with
Coccinelle.

Signed-off-by: Nishka Dasgupta <nishka.dasgupta@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>